In the production of carpeting and, especially, deep-pile carpet, the pile-carrying web is provided with transverse zones which are free from pile and are recurrent, the continuous web being severed or cut into lengths along these zones.
It is known to provide a pile-height detector which responds to the upper surface of the pile and detects changes in the height of the web indicative of the passage of a pile-free zone at which the height of the web corresponds to the thickness of the backing.
The device is provided with a signal generator responsive to the detection of the height difference between the top of the pile and the upper surface of the pile-free zone to initiate the cutting operation.
The web is transported past the detector along a transport path by any conventional conveying or displacing means.
In earlier devices, the detector was constituted by a member which dropped into the recess formed by the pile-free zone and could have a length up the length of the pile-free zone and a width slightly less than that of the pile-free zone.
In general, the cutting operation consisted of halting the displacement of the web and shifting a cutting head across the width thereof.
The detector was disposed above the transport path and generally adjusted by hand so as to lie above the tips of the pile, the sensor dropping into the pile-free zone when the latter reached the detector.
Various problems were encountered with this device not the least of which was the need for repositioning the device for various thicknesses of carpeting and pile heights.